Power tools including an electrical motor unit are often provided with electrical power from a battery unit. FIG. 1 schematically shows an example of such a power tool 100. The power tool 100 includes a body/housing 101 and a shaft/spindle 102. An electrical motor unit is used for driving the shaft 102. The electrical motor is driven by a battery unit 104. The battery unit 104 can be mounted at a handle 103 of the power tool, as shown in FIG. 1, but can also be mounted on other parts of the power tool 100. However, the battery unit 104 can also be located separated from the power tool 100, and the electrical power can then be provided to the electrical motor unit by one or more cables that are connected between the external battery unit and the power tool 100. The power tool 100 further includes a number of parts not shown in FIG. 1, as is understood by a skilled person.
Power tools of today, such as nut-runners, generally have problems relating to the size and weight of the power tool. There is generally a demand for reducing the size and/or the weight of the power tools, since a small and lightweight power tool is very useful for the consumer, because it is easy to transport and also practical to use, since it is not too heavy to hold and handle.
Power tools include a number of parts adding to the size and/or weight of the tool. One part having a big influence on the both the size and the weight of the tool is the battery unit. The performance of the power tool is today directly related to the power being supplied by the battery unit, and is thereby also directly related to the size and weight of the battery unit. For example, both the run-down speed and the torque provided by a nut-runner are directly related to a voltage level of the battery unit. Therefore an efficient and high performing nut-runner today has to be provided with a large and heavy battery pack.
In order to try to adapt the power tool to a current performance demand, while minimizing the size and/or weight of the tool, some prior art solutions have utilized a set of different battery units or batteries having different powers and/or voltages. Thus, depending on the needed performance of the power tool, the user has the possibility to choose a suitable battery unit or battery from this set to be connected to the power tool. Hereby, the size and weight of the power tool can be adapted to the performance demand. Handling of a very powerful power tool, which also is very heavy and large, when a much less powerful, and also much smaller and lighter, tool would have been sufficient can hereby be avoided.
However, the set of battery units that can be used in the power tool must still be carried along with the power tool by a user to achieve adaptability of performance and size of the tool. Also, all battery units have to be charged for the user to be able to adapt the battery supply during work with the tool, which makes this solution not very practical. Also, battery units and/or batteries having different powers and/or voltages are today often provided with different connection interfaces. Thus, a first battery having a first voltage/power may be directly connectable to the power tool while a second battery having a second voltage/power is often not directly connectable to the power tool. It might therefore be difficult to efficiently interchange the batteries, at least without the use of one or more battery adapters.